The present invention relates generally to automatic gearboxes for motor vehicles, of the type in which gear engagement and selection, and clutch operation are all servo assisted. More specifically, the invention relates to an electronically controlled gearbox of the said type.
Automatic gearboxes for motor vehicles are known in the art in which the gear-changing operations are performed entirely by servomechanisms able to perform the engagement, disengagement and selection of the gears, as well as the engagement and disengagement of the clutch. The gear-change operation may be performed automatically by an automatic gear-change control circuit, for example on the basis of the speed of rotation of the engine and the pressure on the accelerator pedal, or alternatively may be performed on the basis of a manual control exercised by the driver. In this latter case it is known as semi-automatic operation.
Gearboxes known in the art have, however, disadvantages due to the non optimal management of the said servo-assisted devices during the gear-change operations. For example, sharp variations in the engine speed and/or drive torque can occur during the disengagement and engagement of the clutch, or noises and knocking in the operations of engaging and disengaging the gears.